The present invention relates to an optical switch system for switching optic signal to be used as an exchanger or switch in an optical communication, and in particular, to an optical switch system for enabling multi-channeling through spatial switching by means of a three-dimensional (3-D) beam steering with using the 2-D matrix and a method for aligning optical axis in such the switch system.
Conventionally, accompanying with development of an optical communication system with using an optic fiber, an optical switch is adopted as a switch or exchanger of such the system. In particular, with the demand for high-speed and large capacity of the communication system, in recent years, the optical switch of multi-channels, so-called an optical switch of matrix-type is applied therein.
The optical switch of so-called a matrix-type is disclosed as an example of a two dimensional (2-D) type, for example, in Japanese Patent Laying-Open No. 2000-330044, wherein connection of optic signals is exchanged or switched over on a plane. However, though this 2-D type optical switch of the conventional art is simple in the structure thereof, it has a limit in multiplexing of channels because of the structure of aligning the optic fibers on the plane, therefore in recent years, there is a strong demand for an optical switch with using the spatial optical connection therein, i.e., an optical switch of 3-D type, which can be manufactured in compact and/or in small-sized.
In such the optical switch of such the spatial connection type, being called by the 3-D, as is shown in Japanese Patent Laying-open No. 2000-247065, for example, a collimated light beam is reflected upon a mirror, so as to switched over the optical connection, in the structure thereof. For this reason, an accurate control in position (or angle) of this reflection mirror is important. However, only with the control in the position of the mirror upon the basis of detected data from an angle sensor attached thereto, it is impossible to fully absorb or dissolve an influence due to thermal deformation of a housing, positional shifting due to secular deterioration or aged change, and further an error of the angle sensor, etc., therefore an efficiency is lowered in connection of optic signals.
Therefore, according to the conventional art, in general, after rough controlling on position of the mirror through an angle control with using such the angle sensor, a portion of the light beam for communication data, which passes through the optical switch, is divided, i.e., from several to several tens % thereof, to be received on a photo diode (hereinafter, by xe2x80x9cPDxe2x80x9d) for estimating an intensity of optical data, through a branch provided on an output side of the system for separation of the optic signal, and the mirror is finely adjusted on the position thereof, so that the light appears the maximum intensity on the light received by the PD for data light intensity estimating.
However, in the optical switch according to the conventional art mentioned above, the difference in the optical intensity between an input light and an output light comes to be the optical loss within said the system. In general, there is provided criteria on the optical intensity of the communication light within the system. If the optical loss is large in the communication path, including the optical switch therein, the optic signal passing through such the optical switch cannot be transmitted, as it is, in the form of an output, in such the case, there is necessity of further operation, such as, amplification for the optical intensity thereof with using an optical amplifier, etc. This brings the optical switch system to be complex in the structure and to be large in sizes thereof. For this reason, it is necessary to reduce the optical loss therein, to be as small as possible.
By the way, as sources of the optical loss in the optical switch of such the spatial connection type, utilizing the mirror therein, there exist various losses, such as, a connection loss in an optic fiber to the optical switch, a loss due to transparency or transmittivity of a collimator lens for collimating the input light, a reflection loss upon the reflection mirror, a loss when re-forming image by the collimated light in an output side, and so on. For this reason, if there is further provided the optical branch for the position control of the reflection mirror mentioned above, since the communication light is consumed, in a part thereof, from a several to several tens percent (%), it constitutes a very large one, of the optical loss in such the optical switch.
Also, in the conventional art, for assuming that the optical connection is in an optimal condition, i.e., the optical intensity is at the maximum, it is necessary to search or find out the mirror position that comes up to the maximum in the optical intensity, while swinging the reflection mirror slightly in a certain degree, so as to change the optic path thereby. However, with this method, the optical intensity is also changed on the communication light during the search operation of the optimal position, therefore there is also a problem, in practical viewpoint.
Accordingly, an object according to the present invention is, for dissolving such the problems of the conventional arts as mentioned above, thus, to provide an optical switch system, having no such the optical loss irrespective of searching of the reflection mirror, with superior optical connection efficiency, being suitable to be used as the switch or exchanger in the optical communications, and further enabling multiplex channel corresponding to the current tendency of high speed and large capacity in the optical communications, and further being able to be compact and small-sized, and also to provide a method for aligning optical axis in such the switch system.
According to the present invention, for accomplishing the above-mentioned object, firstly, there is provided an optical switch system, for switching over plural input lights and plural output lights corresponding thereto through spatial optical connection therebetween, comprising: a first reflection mirror to be directed with an input light and being controllable in position thereof; a second reflection mirror disposed opposite to said first reflection mirror, for reflecting the light reflected on said first reflection mirror, so as to outputted it therefrom; means for controlling positions of said first reflection mirror and said second reflection mirror, respectively; and means for adjusting the position of at least one of said first and second mirrors, which are controller by said controlling means by means of a reference light being substantially different from said input light in wavelength thereof.
Also, according to the present invention, in the optical switch system as mentioned in the above, wherein said position adjusting means adjusts the position of at least the one of said first and second mirrors, so that the input light, reflecting upon said first reflection mirror and propagating onto said second reflection mirror, comes to the maximum in the optical intensity thereof.
Also, according to the present invention, in the optical switch system as mentioned in the above, wherein said position adjusting means adjusts the position of at least the one of said first and second mirrors by means of difference in intensity between the reference light irradiated upon said first reflection mirror and the reference light propagating onto said second reflection mirror.
And, according to the present invention, in the optical switch system as mentioned in the above, wherein in an input side, there are further provided a reference light generator means for generating the reference light therefrom and an optical mixer for mixing the said input light and said reference light to be irradiated upon said first reflection mirror, and in an output side are provided an optic divider for selectively reflecting said reference light thereupon so as to separate it form said input light, and a light receiving means for detecting the intensity of said reference light selected.
Further, according to the present invention, in the optical switch system as mentioned in the above, wherein in an input side, there are further provided a reference light generator means for generating the reference light therefrom, an optic mixer for mixing the said input light and said reference light to be irradiated upon said first reflection mirror and means for collimating said input light while dispersing said reference light selectively, so as to be irradiated upon said first reflection mirror, and in an output side is provided means for selectively detecting irradiating position of said dispersed reference light upon said second reflection mirror, wherein said position adjusting means adjusts the position of said first reflection mirror.
In addition thereto, according to the present invention, in the optical switch system as mentioned in the above, wherein said means for detecting the irradiating position of said dispersed reference light upon said second reflection mirror comprises plural numbers of light receiving elements, being disposed neighboring with each other, around a central portion thereof where a penetrating opening is formed for passing through the input light.
Further in addition thereto, according to the present invention, in the optical switch system as mentioned in the above, wherein said plural numbers of light receiving elements are provided in number of four (4).
Also, according to the present invention, in the optical switch system as mentioned in the above, wherein on a light path after said second reflection mirror, there is further provided a light receiving element having plural numbers of elements, being disposed neighboring with each other, around a central portion thereof where a penetrating opening is formed for passing through the input light, wherein said adjusting means control the position of said second reflection mirror upon basis of an output of said light receiving element.
Also, according to the present invention, in the optical switch system as mentioned in the above, wherein in an input side, there are further provided a reference light generator means for generating the reference light therefrom and means for collimating said input light and superimposing said reference light from said reference light generating means thereon in coaxial manner, so as to be irradiated upon said first reflection mirror, and in an output side is provided light receiving element for selectively detecting said reference light from the light propagating through reflection upon said first and said second reflection mirrors, wherein said position adjusting means adjusts the position of at least one of said first and said second reflection mirrors.
And, according to the present invention, in the optical switch system as mentioned in the above, wherein said light receiving element comprises plural numbers of light receiving elements, being disposed neighboring with each other, around a central portion thereof where a penetrating opening is formed for passing through the input light.
Further, according to the present invention, in the optical switch system as mentioned in the above, wherein said plural numbers of light receiving elements constructing said light receiving element are in number of four (4).
In addition thereto, according to the present invention, in the optical switch system as mentioned in the above, wherein there is further provided means for selectively removing said reference light from the light irradiating upon said light receiving element.
Also, according to the present invention, also for accomplishing the above mentioned object, there is further provided a method for aligning axis of an optic signal, in an optical switch system for switching over plural input lights and plural output lights corresponding thereto through spatial optical connection therebetween, having: a first reflection mirror to be directed with an input light and being controllable in position thereof; a second reflection mirror disposed opposite to said first reflection mirror, for reflecting the light reflected on said first reflection mirror, so as to outputted it therefrom; means for controlling positions of said first reflection mirror and said second reflection mirror, respectively; and means for adjusting the position of at least one of said first and second mirrors, which are controller by said controlling means comprising the following steps of: (a) generating a reference light being substantially different from said input light in wavelength thereof; (b) reflecting both said reference light generated and said input light upon at least one of said first and said second reflection mirrors; and (c) detecting optical intensity of said reference light selectively diverged from said reflection light, and controlling position of at least one of said first and said second reflection mirrors, so that said input light is at maximum in optical intensity thereof.
And, according to the present invention, in the method for aligning axis of an optic signal as mentioned in the above, wherein said steps (a) to (c) are conducted when switching-over operation of said optical switch system.
Further, according to the present invention, in the method for aligning axis of an optic signal as mentioned in the above, wherein in said step (b), said reference light is superimposed with said input light, in coaxially therearound, to be irradiated upon at least one of said first and said second reflection mirrors.
And, according to the present invention, in the method for aligning axis of an optic signal as mentioned in the above, wherein in said step (c), the position of at least of said first and said second reflection mirrors are so controlled that said reference light, being superimposed abound said input light, comes to at a center of at least one of said first and said second reflection mirrors.